1. Field of the Invention
This invention relates to a gas-generating agent particularly a solid gas-generating agent, for use in a ducted rocket engine.
The ducted rocket engine generally burns a gas-generating agent in a primary combustion chamber thereby generating a hot fuel-rich gas, leading this gas into a secondary combustion chamber, and effecting perfect combustion of this gas inside the secondary combustion chamber with the air introduced therein. It is capable of acquiring a greater thrust than the conventional rockets.
2. Prior Art Statement
As the solid gas-generating agent for use in the ducted rocket engine, part of the components of a composite propellant is utilized. It is composed mainly of a binder serving as a fuel and binder, a metallic powder serving as a metallic fuel, and an oxidizing agent. The binders which are usable for the composite propellant include polybutadiene and polyurethane and, as high-energy binders, polyethers possessing an azidomethyl group (Japanese Patent Public Disclosure SHO 62(1987)-265192), for example, the metallic powders which are usable herein include aluminum and boron, for example. The oxidizing agents which are usable herein include ammonium perchlorate, ammonium nitrate, and nitramine, for example.
In order for the ordinary composite propellant to generate a large amount of gas at an elevated temperature, it is essential that the propellant should contain a large amount of an oxidizing agent. When the ordinary composite propellant is used as a solid gas-generating agent in the ducted rocket engine, therefore, the generated gas is substantially wholly burnt in the primary combustion chamber and the gas led into the secondary combustion chamber has only a small amount of fuel component. Thus, the engine is now allowed to fulfill its function fully.
The solid gas-generating agent for use in the ducted rocket engine is required to be so composed as to contain an oxidizing agent component in an amount incapable of inhibiting the combustion of the gas-generating agent and a fuel component in a large amount.
A solid gas-generating agent for use in the ducted rocket engine which abundantly contains, as the metallic fuel, the metallic powders of aluminum, boron, and magnalium, i.e. an alloy of aluminum with magnesium, has been proposed [Japanese Patent Public Disclosure SHO 59(1984)-92992 and Japanese Patent Public Disclosure SHO 61(9186)-127692].
The solid gas-generating agents for use in the ducted rocket engine which specifically disclosed in these Patent Public Disclosures comprise 40 to 50% by weight of metallic fuel, 15 to 20% by weight of hydroxyl-terminating polybutadiene (HTPB) as a combination fuel and binder, and 35 to 40% by weight of ammonium perchlorate as an oxidizing agent.
The conventional solid gas-generating agents for use in the ducted rocket engine which are described above, however, have the problem that they do not easily generate a gas sufficiently rich in the fuel component because they contain 35 to 40% by weight of the oxidizing agent and, as a result, part of the metallic fuel and the binder as a combination fuel and binder are oxidized in the primary combustion chamber. They also have the problem that since the burning rate is low and consequently the amount of gas to be generated is small and, moreover, the pressure exponent is low, it is difficult to control the flow volume of the gas from the primary combustion chamber by varying the surface area of the nozzle throat of the primary combustion chamber.
When the surface area of the nozzle throat is decreased to one half of the initial value, the flow volume of the gas from the nozzle increases only to about 3.2 times the initial value where the pressure exponent is 0.4 and it increases to about 10.1 times the initial value where the pressure exponent is 0.7. How the relation between the rate of change in the surface area of the nozzle throat and the flow volume of the gas from the nozzle is affected by the change in the pressure exponent, n, is diagrammatically illustrated. For practical purposes, the pressure exponent is desired to be approximately in the range of 0.5 to 0.7.
The inventors have made a diligent study, with due consideration paid to the drawbacks of the conventional gas-generating agent for use in the ducted rocket engine, to acquire the knowledge that a specific aliphatic polyether possessing an azidomethyl group in the side chain thereon as shown by the formula to be described herein below burns without containing any oxidizing agent and, therefore, a gas-generating agent containing this polyether is characterized by burning stably and generating a gas containing a fuel component in abundance, and exhibiting a high burning rate and a high pressure exponent. The present invention has been accomplished as the result.